diff --git a/arduino-core/src/processing/app/helpers/FileUtils.java b/arduino-core/src/processing/app/helpers/FileUtils.java
index 4f99f48e2..9d138b841 100644
--- a/arduino-core/src/processing/app/helpers/FileUtils.java
+++ b/arduino-core/src/processing/app/helpers/FileUtils.java
@@ -169,7 +169,15 @@ public class FileUtils {
   }
 
   public static boolean isSCCSOrHiddenFile(File file) {
-    return file.isHidden() || file.getName().charAt(0) == '.' || (file.isDirectory() && SOURCE_CONTROL_FOLDERS.contains(file.getName()));
+    return isSCCSFolder(file) || isHiddenFile(file);
+  }
+
+  public static boolean isHiddenFile(File file) {
+    return file.isHidden() || file.getName().charAt(0) == '.';
+  }
+
+  public static boolean isSCCSFolder(File file) {
+    return file.isDirectory() && SOURCE_CONTROL_FOLDERS.contains(file.getName());
   }
 
   public static String readFileToString(File file) throws IOException {
diff --git a/arduino-core/src/processing/app/packages/UserLibrary.java b/arduino-core/src/processing/app/packages/UserLibrary.java
index 941da7ad2..ef24022ab 100644
--- a/arduino-core/src/processing/app/packages/UserLibrary.java
+++ b/arduino-core/src/processing/app/packages/UserLibrary.java
@@ -83,8 +83,7 @@ public class UserLibrary extends ContributedLibrary {
     // "arch" folder no longer supported
     File archFolder = new File(libFolder, "arch");
     if (archFolder.isDirectory())
-      throw new IOException("'arch' folder is no longer supported! See "
-              + "http://goo.gl/gfFJzU for more information");
+      throw new IOException("'arch' folder is no longer supported! See http://goo.gl/gfFJzU for more information");
 
     // Check mandatory properties
     for (String p : MANDATORY_PROPERTIES)
@@ -101,8 +100,7 @@ public class UserLibrary extends ContributedLibrary {
 
       File utilFolder = new File(libFolder, "utility");
       if (utilFolder.exists() && utilFolder.isDirectory()) {
-        throw new IOException(
-                "Library can't use both 'src' and 'utility' folders.");
+        throw new IOException("Library can't use both 'src' and 'utility' folders.");
       }
     } else {
       // Layout with source code on library's root and "utility" folders
@@ -110,11 +108,14 @@ public class UserLibrary extends ContributedLibrary {
     }
 
     // Warn if root folder contains development leftovers
-    for (File file : libFolder.listFiles()) {
-      if (file.isDirectory()) {
-        if (FileUtils.isSCCSOrHiddenFile(file)) {
+    File[] files = libFolder.listFiles();
+    if (files == null) {
+      throw new IOException("Unable to list files of library in " + libFolder);
+    }
+    for (File file : files) {
+      if (file.isDirectory() && FileUtils.isSCCSOrHiddenFile(file)) {
+        if (!FileUtils.isSCCSFolder(file) && FileUtils.isHiddenFile(file)) {
           System.out.println("WARNING: Spurious " + file.getName() + " folder in '" + properties.get("name") + "' library");
-          continue;
         }
       }
     }
@@ -131,8 +132,7 @@ public class UserLibrary extends ContributedLibrary {
     if (category == null)
       category = "Uncategorized";
     if (!CATEGORIES.contains(category)) {
-      System.out.println("WARNING: Category '" + category + "' in library " +
-              properties.get("name") + " is not valid. Setting to 'Uncategorized'");
+      System.out.println("WARNING: Category '" + category + "' in library " + properties.get("name") + " is not valid. Setting to 'Uncategorized'");
       category = "Uncategorized";
     }